The Induction, Formation, and Establishment of Giant Cell in Plant-Parasitic (Meloidogyne Spp.)-Host Interactions: A Molecular and Cellular Basis
Abstract
Root-knot nematodes, (RKN) are obligatory endoparasites of over 3000 plant species, causing $70 billion in annual economic losses globally. The second stage juveniles hatch from the eggs invade the root apex and inject pathogen effectors that induce specialized feeding cell called Giants cell that are large multinucleated cell formed, due to repeated cycles of mitosis without cytokinesis and served sole source of feeding site for rootknot nematode. The ability RNN induce and maintain giant cell is an example of elaborated mechanism of parasitism (or survival adaptation) of RKN-host interaction. Therefore, understanding cellular & molecular mechanism used by RKN to establish feeding cell (giant) might provide idea of how to develop new and safe disease control strategies. In this review, therefore, we have summarized recent advance in molecular and cellular basis of giant cell induction, development and maintenance.The reviewers have summarized many genes involved in host fundamental process such as cell wall remodeling, cell cycle control, cytoskeleton organization as candidates for giant cell induction, development and maintenance. For example, transcriptional activation of the cell cycle markers cdc2a observed in Arabidopsis roots and in tomato expansin, the gene LeEXPA5 has been shown to be expressed in gall cells adjacent to the giant cells. The endo-b-D- glucanasesare also implicated in feeding cell formation. The actin cytoskeleton has a unique arrangement during the formation of giant cell expansion. A significant amount of odd, randomly orientated actin bundles and cables occur in the genes AtFH1, AtFH6, and AtFH10, which are uniquely activated in giant cells. In conclusion, the regulation of host gene involved in cell cycle, cell wall expansion and cytoskeleton remodeling can be considered as a signature for giant cell induction, development and maintenance.
Keywords: Meloidogyne spp., giant cell formation, genes, cell cycle control, cytoskeleton organization, molecular basis, cellular basis.
INTRODUCTION: Root-knot nematodes (RKN), also known as Meloidogyne spp., are obligatory, sedentary endo- parasites of more than 3000 plant species. They are responsible for significant crop losses that cost the global economy $70 billion annually.